macOS 10.13: "Scheduling the NSURLDownload loader is no longer supported." - cocoa

Question

Running my macOS app in macOS 10.13, I see printed to the console:
Scheduling the NSURLDownload loader is no longer supported.
What does this mean?

Answer 1

The Sparkle Updater seems to be the culprit in the instances I have found. I guess the Sparkle dev team will be on to it and hopefully we'll no longer see the message after Sparkle is updated.

Answer 2

It appears to mean You have just created an instance of the deprecated class NSURLDownload.
To show this, create a new Cocoa command-line tool project in Xcode and replace the code in main.m with the following:
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSURL* url = [[NSURL alloc] initWithString:#"https://example.com"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
cachePolicy:NSURLRequestReloadIgnoringCacheData
timeoutInterval:30.0];
NSLog(#"Will print strange sentence to console") ;
[[NSURLDownload alloc] initWithRequest:request
delegate:nil];
NSLog(#"Did print strange sentence to console") ;
}
return 0;
}
Build and run. I get the following result in console (timestamps removed):
Will print strange sentence to console:
Scheduling the NSURLDownload loader is no longer supported.
Did print strange sentence to console
I would say the "fix" is to replace the deprecated NSURLDownload with NSURLSession.

Answer 3

You can correct it directly in the source code for Sparkle. Update SUAppcast.m file at line 82 by replace the NSURLDownload with the following:
NSURLSessionDownloadTask *downloadTask = [[NSURLSession sharedSession] downloadTaskWithRequest:request completionHandler:^(NSURL *location, __unused NSURLResponse *response, NSError *error) {
if (location) {
NSString *destinationFilename = NSTemporaryDirectory();
if (destinationFilename) {
// The file will not persist if not moved, Sparkle will remove it later.
destinationFilename = [destinationFilename stringByAppendingPathComponent:#"Appcast.xml"];
NSFileManager *fileManager = [NSFileManager defaultManager];
NSError *anError = nil;
NSString *fromPath = [location path];
if ([fileManager fileExistsAtPath:destinationFilename])
[fileManager removeItemAtPath:destinationFilename error:&anError];
BOOL fileCopied = [fileManager moveItemAtPath:fromPath toPath:destinationFilename error:&anError];
if (fileCopied == NO) {
[self reportError:anError];
} else {
self.downloadFilename = destinationFilename;
dispatch_async(dispatch_get_main_queue(), ^{
[self downloadDidFinish:[[NSURLDownload alloc] init]];
});
}
}
} else {
[self reportError:error];
}
}];
[downloadTask resume];